1. Field of the Invention
Aspects of the present invention relate to information recording media, and more particularly, to an information recording medium, a recording/reproducing apparatus, and a recording/reproducing method, by which data replacement upon logical overwrite (LOW) occurring in a spare area or in a user data area may be efficiently managed.
2. Description of the Related Art
Rewritable information recording media generally include a spare area in a portion of a data area to achieve defect management. In other words, when defective data is detected while user data is being recorded in a user data area (an area left by excluding the spare area from the data area) or while data recorded in the user data area is being reproduced, a replacement of the defective data is recorded in the spare area.
In write-once information recording media, such defect management method is applied to logical overwrite (LOW). Logical overwrite is a technique that generates the same effect as the rewrite of data to write-once information recording media. In other words, to update data already recorded in the user data area, the recorded data is treated as defective data, and replacement data that replaces the recorded data is recorded in the spare area. Accordingly, the logical address of the data already recorded in the user data area is still used as the logical address of the replacement data, although the physical address of the replacement data is different from the physical address of the already-recorded data. Hence, a host can detect that the data already recorded in the user data area was overwritten, because the host accesses only a logical address. Thus, the host can easily manage the write-once information recording media.
However, a method of recording update data in an unrecorded area of a user data area instead of a spare area and providing replacement information (i.e., defect entry information) has been used to achieve LOW based on defect management to fully utilize the capacity of a write-once information recording medium.
This recording of a replacement in the unrecorded area of the user data area to achieve LOW complicates the recovery of replacement data destroyed by power failure or an error of replacement information. Where an area in which a replacement of defective data or a replacement for LOW is recorded is limited to a spare area, a replacement block exists only in the spare area. Hence, replacement data can be recovered by searching only the separate spare area for replacement blocks. However, as a user data area is used as the area in which a replacement of defective data or a replacement for LOW is recorded, there appears a need to classify the blocks recorded in a user area on an information recording medium into user blocks (original data block that is not replaced by a new block) and replacement blocks. In addition, where replacement data is recorded in the user data area, predetermined rules are needed to easily recover the replacement data.
In summary, where a replacement of user data for LOW cannot be recorded only in a spare area but also in a user data area, user blocks cannot be distinguished from replacement blocks due to the absence of a physical boundary between a physical area in which the user blocks are recorded and a physical area in which the replacement blocks are recorded. Particularly, where a user block is replaced by a replacement block, and the replacement block is replaced again, a final replacement block cannot be identified. Finally, a drive system cannot distinguish between a case where a replacement block is replaced again and a case where a block is recorded in a physically unrecorded space in response to a command to record data in a space that is physically recorded with data but logically unrecorded.
The above mentioned conventional problems will now be described with reference to FIGS. 1A through 1C. Referring to FIG. 1A, in case 1, a 1st update of original data A is recorded in track #1, and a 2nd update is recorded in track #2. In case 2, a 1st update of original data A is recorded in track #2, and a 2nd update is recorded in track #1. In case 3, a 1st update of original data A is recorded in track #2, and a 2nd update is recorded in a spare area SA. In case 4, a 1st update of original data A is recorded in a spare area, and a 2nd update is recorded in track #2.
As shown in FIG. 1A, although only data A″ obtained by updating original data A twice exists in a logical space, a final update, namely, data A″, is recorded in different locations in a physical space in cases 1 through 4.
Referring to FIG. 1B, in case 5, original data, data A, a first update of the data A, data A′, and a second update of the data A, data A″, are sequentially recorded in a physical volume space of track #2 in a user data area. Referring to FIG. 1C, in case 6, original data, data A, a first update of the data A, data A′, and original data, data B, are sequentially recorded in a physical volume space of track #2 in a user data area.
As shown in cases 5 and 6, although physical recording statuses in cases 5 and 6 are the same, recording statuses of actual information recording mediums in cases 5 and 6 are different. Thus, a block to be recorded needs to include specific information so that a drive system can distinguish two different cases.